The only valid arguments for a Publish REQUEST are:MessageMessageAttributesMessageStructurePhoneNumberSubjectTargetArnTopicArn

You say: The correct answers are: Subject, MessageId, Timestamp

And your answer has a screen cap from AWS. But this is a Publish CONFIRMATION return message. That's totally different.

A publish request couldn't have a messageId or Timestamp as an argument (An argument is a parameter I send to my SNS topic to publish a message). The messageId and timestamp are data points that SNS creates and returns to me in a confirmation message.

I'm guessing that since my reference to the screen cap is now a broken link that things are being fixed?

FYI, I took the CDA Exam this morning and passed with a 96%. The very last question may have been similar this question. But the choices were related to reference to an actual Publish Request. So if you learn the attributes of a publish request you will do okay.